DIRECT COMPARISON OF LEVELS OF GENETIC-VARIATION IN TOMATO DETECTED BY A GACA-CONTAINING MICROSATELLITE PROBE AND BY RANDOM AMPLIFIED POLYMORPHIC DNA

In this study, a direct comparison was made of the ability of four sel ected random amplified polymorphic DNA (RAPD) primers and a GACA-conta ining microsatellite probe to detect genetic variation in Lycopersicon . Of the 89 RAPD primers initially tested, 85 showed differences betwe en a representative of Lycopersicon pennellii and L. esculentum, but o nly 4 distinguished among three L. esculentum cultivars. These four pr imers were subsequently tested on representatives of six Lycopersicon species. In pairwise comparisons of species, all or 14 of the 15 combi nations could be distinguished by single primers. When the primers wer e tested on 15 L. esculentum cultivars, 90 of the 105 combinations cou ld be distinguished by the four primers together. Finally, none of 118 tested primers showed reproducible differences among calli or progeny of regenerants from tissue culture, although some of the plants had i nherited morphological mutations. The probe pWVA16, which detects GACA -containing microsatellites, could distinguish in TaqI-digested DNA th e representatives of Lycopersicon species as well as all the L. escule ntum cultivars tested. The probe was unable to detect polymorphisms am ong calli and the progeny of regenerants from tissue culture. An analy sis of the results showed that the four selected RAPD primers were abl e to detect polymorphic bands among species at a frequency of 80%, and among cultivars at a frequency of 44%. In contrast, the microsatellit e probe detected polymorphic bands at a frequency of 100 and 95%, resp ectively. The GACA-containing probe did not detect any common bands am ong the representatives of the six species, while band sharing with RA PDs was 48%. These results indicate that the two methods detect two ty pes of DNA that differ in their degree of variability.